Re: /var/log/messages doesn't have crash info when kernel gets panic/oops/crash

Dharmosoth Seetharam
2009-06-16T04:41:35Z

Hi,

I have experimented few things and results are below.

Case 1) echo 0 > /proc/sys/kernel/panic_on_oops
When BUG/oops occurred it is able to log the diagnostics to /var/log/messages
and then continue(not switching to dump-saving kernel).

What I am looking is - I want both the things to be happen.
that is - it should log the appropriate messages in /var/log/messsages and
should be able to take kernel dump.

case 2) In general, When panic has occurred we won't log any type of messages in
/var/log/messages ... am I right ?
If KEXEC is enabled and dump-saving kernel is loaded then
will switch to it and save the kernel dump.

I have added the dump_stack() function call in the panic() function
before calling crash_kexec with few seconds of delay. It is behaving
like randomly (ie. some time stack traces are logged in /var/log/messages and
not for rest of the time)

What I am looking is - I want to log the appropriate messages in /var/log/messages
and then switch to dump-saving kernel.

case 3) In general, When die/nmi_die called we used to log the appropriate messages in /var/log/message
and then saving kernel dump will be depends on KEXEC enable and loading dump-saving kernel.
--- am I right ?

I have added the delay in die() function with few seconds before calling crash_kexec()
But I never seen messages logged in /var/log/messages, I can see those on serial console.

Here also my intention is want both, ie. log the appropriate messages in /var/log/messages
and then take the action as per KEXEC enabled.

Please advice me, What we can do to achieve those things.

Thanks for helping me here.

regards,
Seetharam

> -----Original Message-----
> From: nhorman@redhat.com
> Sent: Sat, 13 Jun 2009 14:07:36 -0400
> To: dseetharam@inbox.com
> Subject: Re: /var/log/messages doesn't have crash info when kernel gets
> panic/oops/crash
>
> On Fri, Jun 12, 2009 at 11:01:35PM -0800, Dharmosoth Seetharam wrote:
>>
>> Hi Neil,
>>
>> Thanks for your quick reply.
>>
>> What you have suggested is nice when we got/save crash dump (i.e vmcore)
>> What if we failed to save/capture vmcore info or vmcore is corrupted
>> etc. then we dont get any information
>> regarding the panic/crash/oops at anywhere?
>>
> If the vmcore is corrupted to the point where makedumpfile can't extract
> the
> dmesg log, then its certain that syslog wouldn't have been able to write
> anything to /var/log/messages either. As a last resort you can try run
> strings
> on the corrupted vmcore and see if the dmesg log is still in there
> somewhere.
>
> If you forgot to capture the vmcore, theres not much more help I can give
> you,
> Im afraid. You'll just have to make sure you capture it next time. If
> you only
> need the backtrace, and don't want the rest of the vmcore, you can make
> kdump
> just run makedumpfile --dump-dmesg /proc/vmcore /var/log/oops.txt
>
> Neil
>

>>
>>
>>
>> Thanks and Regards
>>
>> Seetharam
>>
>>
>>> -----Original Message-----
>>> From: nhorman@redhat.com
>>> Sent: Fri, 12 Jun 2009 16:05:13 -0400
>>> To: dseetharam@inbox.com
>>> Subject: Re: /var/log/messages doesn't have crash info when kernel gets
>>> panic/oops/crash
>>>
>>> On Fri, Jun 12, 2009 at 01:25:49AM -0800, Dharmosoth Seetharam wrote:
>>>> Hi,
>>>>
>>>> I have encounter a problem called /var/log/messages does not contain
>>>> any
>>>> information
>>>> on kernel crash dump.
>>>>
>>>> Prior to enabling KEXEC we saw stack traces and bug info etc in
>>>> /var/log/messages.
>>>> After enabling KEXEC feature those info was missed.
>>>>
>>>> How can we get those missed info in /var/log/messages even when KEXEC
>>>> feature is enabled.
>>>>
>>>> Any help will appreciate.
>>>>
>>> run crash on the resultant vmcore file that kexec can produce/save and
>>> get the
>>> dmesg log out of it.
>>> alternatively you can use makedumpfile with the --dump-dmesg log
>>>
>>> Neil
>>>
>>>>
>>>> Thanks and Regards
>>>> Seetharam
>>>>
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